Energy consumption for district heating and cooling purposes constitutes a significant share of the European Union’s total energy demand. Therefore, efficiency measures should be introduced into all three parts of district heating systems, i.e., heat sources, distribution networks and the final consumers. Also, the increase of energy generation from renewable energy sources is promoted at the European Union level and the research on sustainable energy systems is progressing. With the development of technologies energy efficiency and renewable energy based solutions are gradually introduced into district heating systems, thus moving towards 4th generation district heating systems. Thus the aim of this Thesis is to provide a structured, multi-perspective methodology based on parsimony principle (also Ockham's razor) that can be used to assess the transition from an existing DH system to the 4th generation district heating systems system. The developed methodology can be used to elaborate and compare several potential DH development scenarios. The following objectives are set to be accomplished within this research: to analyse existing district heating system and to evaluate technical, economic, socioeconomic, environmental and institutional indicators; to create the holistic methodology in order to evaluate most suitable solution for the transition of district heating systems towards 4th generation district heating systems. The multi-perspective analysis provides the methodology with combines empirical study tools, system dynamics, multi-criteria decision-making framework, economic and policy analysis. The results show that decision makers need to concentrate the attention on strategic actions - governmental regulation, taxes, subsidies, changes in energy price depending on prioritised scenario. The implementation of policy instruments for energy system planning allows achieving 4th generation district heating system. Although the model was based on Latvian specific technological substitution process, the developed multi-perspective framework could be applied to other DH systems. This Doctoral thesis is based on the thematically unified 14 scientific publications. Those publications are published in various scientific periodicals. 14 Articles are presented in SCOPUS database (cited 37 times) and 7 - in ISI Web of Science database (cited 13 times). The goal of these publications is to transfer and approbate the framework of multi-perspective methodology to assess the transition of existing DH system toward 4th generation district heating.